The present invention relates to a reinforcement that reduces the stresses in long cracks in automobile windshields in particular, which have been repaired with a filling of repair material, such as a resin, to suppress failures of the repair material in the crack.
Various windshield repair devices have been advanced, and some are provided for filling long cracks in windshields. For example, U.S. Pat. No. 5,512,116 illustrates a repair device and process for long cracks, by filling the crack with a resin, and in this instance, the disclosure provides a bead of resin bridging the crack near the edge of the windshield. The patent discloses that a higher viscosity resin should be used for the bridge at the edge of the windshield. Merely having a resin "bridge" on the glass does not provide for a sufficient reduction in stress on the resin in the crack to reduce failures from temperature differentials and flexing of the frame that supports the windshield, including the automobile frame.
Repair methods utilizing patches have been advanced for other uses. For example, U.S. Pat. No. 4,859,491 shows a cryogenic heat exchanger having a fissure in the heat exchanger body, that is repaired by filling with an adhesive or sealant and laying a metal patch over the crack, and in a position to span the fissure or crack.
Repair resins for cracks in windshields are also disclosed in U.S. Pat. No. 5,069,836 to Werner et al. The resin used can be ultraviolet light cure resin. Such resin is preferred in many instances. The injection of resin into a long crack for repair is done in accordance with the previously taught repair procedures.
These previously taught procedures are widely used for repairing cracks in glass, and in particular windshields, and they do use a reasonably strong and optically acceptable resin. The resin is introduced in the crack and cured to bond the glass back together at the break. After the repair, the windshield is subjected to stress resulting from such causes as flexing of the automobile frame and temperature variations. A common result is that the crack repair fails, almost always initially at the edge of the windshield, and then the failure usually propagates along the repaired crack, ruining the repair. Repair resin bonds are usually not as strong as the original undamaged windshield.
The present invention provides a reinforcement that will suppress such failures and increase the effectiveness of existing repair procedures.